Most IC devices have a support structure or lead frame having a plurality of leads extending toward the center of the lead frame, at which a bar pad is typically disposed. The bar pad may be attached to the lead frame structure by at least one tie bar. The leads are joined by at least one dam bar. Dam bars keep the leads connected to the lead frame during an IC device assembly process while preparing to mount a chip, e.g., a semiconductor chip, on the bar pad. The dam bar(s) referred to above are generally provided at the outer ends of the leads. Dam bar(s) are removed by a punch or die tooling operation before the assembly process is completed.
Lead frames may be of various sizes depending upon the size of the chip and the number of wire bonds that are made between the leads and the bond pads of the chip. Moreover, leads to be connected to the chip are spaced around the chip, such that they are adequately sized and sufficiently spaced to receive a wire bond from the chip. For this reason, lead frames commonly may have connecting leads on at least two sides of the bar pad, and many lead frames have connecting leads on four sides. Lead frames are usually manufactured in long strips which-may include many individual units. The long strips are wide enough to accommodate from one to as many as five lead frames, for example.
Before the leads are connected to the chip, a cavity mold may be provided to surround and protect the area in which the chip and the wire bonds are disposed. Such cavity molds are generally manufactured by molding, e.g., injection molding, a plastic to cover the middle portion of the leads. When the plastic hardens, the mold may also serve as a support structure for the IC device. The mold, however, is placed in the middle portion of the lead because the inner portion of the leads, i.e., the lead fingers, receive the wire bonds from the chip's bond pads and the outer lead ends are used to join the IC device to other components. If plastic covers the inner or outer portions of the leads, electrical connections with those portions of the lead are inhibited.